In climacteric women, anxiety, depression tension and irritability begin during the perimenopause and can be correlated to reduced estrogen levels and estrogen replacement therapy has been recommended for the treatment of these symptoms (Malleson J., Lancet, 2: 158, (1953); Wilson et. al., J. Am. Geriatric Soc., 11: 347 (1963)). The mechanism for protective effects of estrogen in this case is unknown, but may be related to potential effects of estrogen on biogenic amines such as serotonin (Aylward M., Int. Res. Communications System Med. Sci., 1: 30 (1973)). To this regard circulating serotonin is reduced in post-menopausal women (Gonzales G., et. al., Maturitas 17: 23-29 (1993)), and serotonin (as well as several other biogenic amines) have a putative role in behavioral depression.
Phillips and Sherwin (Psychoneuroendocrinology, 17: 485-495 (1992)) reported that in surgically menopausal women given estrogen, scores in immediate and delayed recall tests are greater than in similar women not given estrogen. Two potential hypotheses might explain this effect. There is some evidence that partial estrogen agonists (or anti-estrogens) such as tamoxifen interact with the muscarinic receptor (Ben-Baruch G., et. al., Molec. Pharmacol. 21: 287-293 1982), and muscarinic agonists (M.sub.2) are known to produce positive effects in a number of memory associated tasks and may have clinical relevance in Alzheimer's Disease. Another interesting possibility may be linked to neurokinins such as Substance P, which are known to have neurotrophic as well as memory-promoting effects (Thoenen H., Trends in Neuroscience, 14: 165-170 (1991); Huston J. et. al., Neurosci. Biobehav. Rev. 13: 171-180 (1989)), thus, through an effect either at a neurotransmitter receptor in the CNS or at a neuropeptide receptor, a tissue selective estrogen agonist/antagonist could produce memory and cognitive enhancing effects. Such an activity would most relevantly be assessed in man, but a variety of animal models (i.e. maze learning, extinction etc.) are available for preclinical testing.
Perhaps the most frequent CNS related problem in climacteric women is the occurrence of hot flushes. While this undoubtedly is a somatic effect mediated by effects on the microvasculature, current evidence points strongly in the direction of CNS initiated effect (Lomax P., et. al., Pharmac. Ther. 57: 347-358 (1993)). Therefore, a tissue selective estrogen agonist/antagonist like raloxifene might offer the ideal therapy providing the desired effect in the absence of untoward side effects on reproductive tissue.